Method of producing ferro-chromium



Patented July 16, 1935 PATENT. OFFICE 2,008,055 METHOD or rnonucmoFERRO-CHBOMIUM Virginie Angelini, Milan, 'Italy No Drawing.' ApplicationApril 20, 1932, Serial No- 606,530. In Belgium April 28, 1931 1 Claim.

This invention relates to a new and improved method of producingferro-chromium, which needs no further refining operation, by employingreducing agents such as aluminium, ferro- 5 silicon andcalcium-silicide.

It has already been proposed to produce ferrochromium from chromium orecontainingchromium oxide by the employment of exothermic reducing agentssuch as aluminium, ferro-silicon, and calcium-silicide. It has also beenproposed to make use of a mixture of the aforesaid reducing agents forproducing the metal alloys in order to obtain special efiects in thereduction of metal oxides.

1 have found that in order to obtain a completely pure product in oneoperation, thus to be ready for the production of the rustlessferrochromium it will be necessary to make use of a determinedquantitative proportion of the chromium ore and the reducing agents.

According to my invention I employ for the production of ferro-chromiumwith a high chromium content the following mixture:-

65% chromium ore (containing 48% of CrzOs), 23% calcium silicide,"4%aluminium, 4% fluorspar, 2% ferro-silicon and 2% lime.

Making use of the mixture composed as described, I obtain a completelypure product in one operation which needs no further refining operation.

If I merely employ a mixture of reducing agents but not in thedetermined quantitative proportions as indicated above, it is notpossible to obtain a product free from all impurities such as excess ofthe reducing agents.

For carrying out my invention any type of furnace may be used as long asit iscapable of keeping in complete fusion the material being usedduring the whole operation. An electric furnace with electrodes servesthe purpose. It is also possible to use an open furnace; any troughturnace, monophase of three-phase with or without a conducting basesimilar to, that employed in the manufacture of ferro-silicon.

As an example a furnace is fed with a mixture 5 of 1000 kg. composed of:650 kg. of chromium ore containing 48% of chromic oxide CI'2O3, 230 kg.calcium silicide, 40 kg. aluminium, 40 kg. fiourspar, 20 kg.ferro-silicon and 20 kg. lime.

When this mixture has become fluid and reaches the temperature of 1600C. (operation which requires about one half to two hours) one hasalready an alloy having a high content of chromium, or to be preciseabout chromium and about 0.23 carbon, traces of silicon, sulphur andphosphorus, and the rest iron. The quantity of this alloy will be about240 kg.

If this ferro-chromium is to be used for the production of the rustlesschromium iron or rustless chromium steel, it can be introduced into aniron bath, for instance a closed furnace contain-- ing 850 kg. fusediron with a carbon content not exceeding 0.1%, the composition of thefinal product will be of about 0.14-0.16 carbon, 12-14% chromium andtherest iron.

In carrying out this second part or the production of rustless chromiumiron or steel it is necessary to provide a protective slag, whosecomposition has for its object the protection of the iron bath fromimpurities caused by the carbon owing to the contact of the electrodeswith the bath.

. I claim:--

A method of producing ferro-chromium which needs no further refiningoperation by employing a mixture of exothermic reducing agents charac-35 terized by the feature that a mixture is used composed of of chromiumore containing 48% of CrzOa, 23% calcium silicide, 4% aluminium, 4%fluorspar, 2% of ferro-silicon and 2% of lime.

' VIRGlNIO ANGELINI.

